Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
  • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
  • B29C49/06—Injection blow-moulding
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/82—Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/86—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure
  • A61F2/90—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure
  • A61F2/91—Stents in a form characterised by the wire-like elements; Stents in the form characterised by a net-like or mesh-like structure characterised by a net-like or mesh-like structure made from perforated sheets or tubes, e.g. perforated by laser cuts or etched holes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
  • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
  • B29C2049/023—Combined blow-moulding and manufacture of the preform or the parison using inherent heat of the preform, i.e. 1 step blow moulding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
  • B29K2067/04—Polyesters derived from hydroxycarboxylic acids
  • B29K2067/043—PGA, i.e. polyglycolic acid or polyglycolide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
  • B29K2067/04—Polyesters derived from hydroxycarboxylic acids
  • B29K2067/046—PLA, i.e. polylactic acid or polylactide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2031/00—Other particular articles
  • B29L2031/753—Medical equipment; Accessories therefor
  • B29L2031/7532—Artificial members, protheses

Definitions

• Stents are relatively small, as they are often required to be passed through tight confines of anatomical lumens.
• a stent must often have great longitudinal flexibility to allow it to pass through tortuous curves of anatomical lumens.
• Stents typically comprise a fine network of struts which form a tubular scaffold.
• the tubular scaffold must often be capable of being crimped onto a delivery device, such as a balloon, to reduce its size to allow passage through anatomical lumens, and then forcibly expanded by the balloon to an enlarged, deployed state at the desired location within the body.
• the tubular scaffold must be capable of self-expanding from its crimped state at the desired location within the body. After implantation and deployment, the tubular scaffold must have sufficient strength to support surrounding anatomical structures.
• Stents have in the past been made of metals, such as nickel-titanium alloys having shape memory and superelastic properties.
• the advent of polymer stents have presented further design challenges.
• the design of a polymer stent must take into account that, as compared to metal stents of the same dimensions, polymer stents typically have less radial strength and rigidity and less fracture toughness.
• a method and system for manufacturing polymer stents that (a) increase uniformity from stent to stent, (b) allow for tight control of design parameters, such as the thickness and dimension of individual stent struts, and/or (c) increase manufacturing efficiency.
• the present invention is directed to a method and system for forming a polymer endoprosthesis.
• a method comprises forming a stock tube of polymer material in an injection mold, transferring the stock tube from the injection mold to a blow mold, the transferring step performed while the stock tube is at a temperature at or above Tg of the polymer material, and expanding the stock tube in the blow mold in order to form a precursor tube.
• a system comprises an injection mold having an injection mold cavity, a blow mold having a blow mold cavity, and a door movable from an first position to a second position, the injection mold cavity and the blow mold cavity being separated from each other by the door when at the first position, the injection mold cavity and the blow mold cavity being exposed to each other with when the door is at the second position.
• FIG. 2C is a cross-section view of the system of FIG. 2A, showing the system after the polymer resin, referred to as a stock tube, is ejected in a non-molten state directly into a blow mold cavity.
• FIG. 2D is a cross-section view of the system of FIG. 2A, showing the system after the stock tube is radially expanded against an interior surface of the blow mold cavity.
• Methods of deforming the injection molded substrate can involve blow molding.
• blow molding For a description of blow molding, see, for example, U.S. Pub. No. 2009/0001633 of Application No. 1 1 /771 ,967 filed June 29, 2007 and U.S. Pub. No. 201 1/0066222 of Application No. 12/558, 105 filed June 28, 2006.
• the method proceeds to block 15 in which the stock tube is released from the first mold while still at a temperature greater than the glass temperature (Tg) of the polymer material but lower than the melt temperature (Tm) of the polymer material.
• Tg is the temperature at which the amorphous domains of a polymer change from a brittle vitreous state to a solid deformable or ductile state at atmospheric pressure.
• Tg corresponds to the temperature where the onset of segmental motion in the chains of the polymer occurs. Between Tg and Tm rotational barriers exist, however, the barriers are not great enough to substantially prevent segmental mobility.
• the polymer material is at a temperature substantially below Tm when released from the first mold. It is to be understood that the stock tube is in a substantially non- molten state when it comes out of the first mold, even though it is at a temperature at or above Tg. Having the stock tube substantially non-molten helps to ensure that the circumferential wall thickness is not inadvertently altered in the time period between release from the first mold (block 15) and expansion in the second mold (block 25 discussed below). This non-molten state of the stock tube upon release from the first mold is distinct from extrusion processes in which an extruded polymer is substantially molten when it exits an extruder die.
• the stock tube is released from the first mold after the flow of polymer material in the mold cavity has substantially stopped. This condition is distinct from extrusion processes in which the polymer material continues to flow through the extruder cavity while exiting the extruder die.
• the stock tube is placed in the cavity of a second mold, which can be a glass- lined blow mold.
• the cavity has an inner diameter that is greater than the outer diameter of the stock tube.
• the internal fluid pressure of the stock tube is increased, such as by pumping a gas into the stock tube.
• the internal fluid pressure is increased to a level which causes the circumferential wall of the stock tube (i.e., substrate) to stretch and expand radially outward against the surfaces of the second mold cavity, thereby changing the mechanical characteristics of the substrate.
• the surfaces of the second mold cavity limit the outward radial expansion of the circumferential wall.
• this step can be performed while the stock tube is still at a temperature substantially above room ambient temperature due to heat from injection molding.
• this step can be performed while the stock tube is at a temperature substantially below ambient room temperature, such as in situations where the stock tube has been actively cooled or quenched within the first mold or upon removal from the first mold.
• Injection mold 100 includes cavity 102 into which molten polymer resin is injected through gate 104.
• the cavity is configured to produce a stock tube.
• the cavity is cylindrical in shape and is bounded by inner circumferential surface 106 and outer circumferential surface 108 of mold 100.
• the distance between circumferential surfaces 106 and 108 defines the thickness of the circumferential wall of the resultant stock tube.
• Outer circumferential surface 108 defines a maximum diameter 109 of injection mold cavity 102.
• the size and shape of the exterior surface of the resultant stock tube will correspond to the outer circumferential surface 108.
• Inner circumferential surface 106 is provided by mold core 1 10 in the shape of a cylindrical rod.
• the size and shape of the interior lumen of the resultant stock tube will be that of mold core 1 10.
• movement of door 1 14 allows the non-molten polymer resin, referred to now as stock tube 1 16, to be released from injection mold 100 and placed into blow mold 120.
• Injection mold 100 and blow mold 120 are connected to each other such that movement of door 1 14 exposes stock tube 1 16 to cavity 122 of blow mold 120.
• injection mold cavity 102 and blow mold cavity 122 form a common, enlarged cavity that is substantially sealed from the external, ambient environment by the interconnected housings 101 and 121 of injection mold 100 and blow mold 1 12.
• With door 1 14 open injection mold cavity 102 and blow mold cavity 122 are exposed to each other.
• ejector 1 19 pushes stock tube 1 16 out of injection mold cavity 102 and directly into blow mold cavity 122.
• Ejector 1 19 can be pneumatically or electrically controlled.
• Stock tube 1 16 is transferred from injection mold cavity 102 into blow mold cavity 122 while shielded from the external, ambient environment.
• FIG. 2E shows precursor tube 1 34 after having been removed from blow mold
• precursor tube 134 can be carried on cylindrical mandrel 136 and placed adjacent cutter 138 for removing portions of precursor tube 134 to form a network of stent struts.
• Perforation 139 has been made by cutter 138 through precursor tube 134. With removal of material, precursor tube 134 is transformed to a stent having a network of stent struts.
• Mandrel 136 is inserted within precursor tube 134 and can be connected to rotation and slide motor and gear assembly 40 under computer numerical control (CNC). Relative movement between mandrel 136 and cutter 138 can be programmed into a CNC software application operating within electronic controller 142 to provide the desired pattern of stent struts.
• CNC computer numerical control
• FIG. 3B shows two halves of injection mold 200 separated to expose mold cavity
• Stock tube 1 16 is in a substantially non-molten state when it is ejected from injection mold 220. In some embodiments, stock tube 1 16 is at a temperature between Tg and Tm when ejected from injection mold 220. In alternative embodiments, stock tube 1 16 is at a temperature below Tg when ejected from injection mold 220.
• Blow mold 220 has an interior diameter 226 which is greater than the maximum outer diameter 209 of the circumferential wall of stock tube 1 16 to allow for radial expansion of the circumferential wall. Interior surface 224 of blow mold 220 limits radial expansion of the circumferential wall.
• blow molding including the application of heat is performed as described in U.S. Pub. Nos. 2009/0001633 and/or 201 1 /0066222.
• FIG. 3D shows the result after gas is pumped into the interior of stock tube 216.
• precursor tube 234 can be carried on cylindrical mandrel 236 and placed adjacent cutter 238 for removing portions of precursor tube 234 to form a network of stent struts. Perforation 239 has been made by cutter 238 through precursor tube 234. With removal of material, precursor tube 234 is transformed to a stent having a network of stent struts.
• Mandrel 236 is inserted within precursor tube 234 and can be connected to rotation motor and gear assembly 240a and slide motor and gear assembly 240b under computer numerical control (CNC). Relative movement between mandrel 236 and cutter 238 can be programmed into a CNC software application operating within electronic controller 242 to provide the desired pattern of stent struts.
• CNC computer numerical control
• the polymer material or resin can be any synthetic or naturally occurring polymer suitable for implantation.
• the material can be selected from the group consisting of poly(L-lactide) (“PLLA”), poly(L-lactide-co-glycolide) (“PLGA”), poly(L-lactide-co-D-lactide) (“PLLA-co-PDLA”) with less than 10% D-lactide, and PLLD/PDLA stereocomplex, and PLLA-based polyester block copolymer containing a rigid segment and a soft segment, the rigid segment being PLLA or PLGA, the soft segment being PCL or PTMC.
• material is removed from the precursor tube to transform the precursor tube to a stent having stent struts arranged in any pattern.
• the stent struts can have the patterns described in U.S. Pub. No. 2008/0275537 of Application No. 12/1 14,608 filed May 2, 2008 and U.S. Pat. No. 7,476,245 issued January 13, 2009.
• the pattern can include stent struts arranged in a repeating pattern of W-shaped cells as described in Pub. No. 2008/0275537 or in a repeating pattern of hour-glass shaped cells as described in Pat. No. 7,476,245.
• the shape of the cells can correspond to perforations 139 and 239 in FIGS.
• the first mold or the injection can have an annular mold cavity having inner diameter ID and outer diameter OD and the second mold or the blow mold can have a cylindrical mold cavity having a diameter D.
• the amount of radial expansion which the stock tube undergoes depends upon the dimensional relationship between the two mold cavities. Without limitation, the following approximate dimensions for ID, OD, and D can be used.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)
• Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
• Materials For Medical Uses (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Citations (11)

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• 2011
  • 2011-05-24 US US13/114,941 patent/US8747728B2/en not_active Expired - Fee Related
• 2012
  • 2012-05-23 JP JP2014512076A patent/JP6058641B2/ja not_active Expired - Fee Related
  • 2012-05-23 EP EP12725238.5A patent/EP2714369B1/en not_active Not-in-force
  • 2012-05-23 CN CN201280031685.5A patent/CN103619562B/zh active Active
  • 2012-05-23 WO PCT/US2012/039164 patent/WO2012162402A1/en not_active Ceased
• 2014
  • 2014-05-02 US US14/268,396 patent/US20140239558A1/en not_active Abandoned

Patent Citations (12)

Non-Patent Citations (1)

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